The issue that would develop with a required ethics course would be that the state cannot completely prescribe morals. Religious freedom requires a certain degree of autonomy there, as do political impartiality requirements. Also, any quality course of philosophy is going to also expose students to thinkers like Robert Wolff, who believe that the individual defines morality. I don't know when you last interacted with freshmen, but I don't think most of them are mature enough, or have seen enough practical applications of philosophy in other subjects to have a philosophy class be successful. Finally, national legislation of education requirements can be both controversial and difficult to pass/implement.